1. Field of Invention
The present invention relates to a redistribution process. More particularly, the present invention relates to a redistribution process using benzocyclobutene for the dielectric layer.
2. Description of Related Art
A redistribution process basically redistributes the Contacts (usually conductive bonding pads) on a wafer to a new pattern using a redistributed trace layer. Normally, in a flip-chip attachment, the periphery I/O bonding pads are redistributed to an area array pattern. Further, the redistributed Contacts are terminated with solder bumps for external connection. Besides forming bumps on the above Contacts, the redistributed Contacts can also be terminated with bonding pads.
In a conventional redistribution process, copper is typically used for the connective traces and the dielectric layer is formed with polyimide or benzocyclobutene. However, the binding between benzocyclobutene and copper is poor when benzocyclo-butene is used as the dielectric layer. Therefore, when a benzocyclobutene layer is formed over a copper trace layer, the peeling of benzocyclobutene during the development process is resulted, adversely affecting the manufacturing process.
The conventional redistribution process is illustrated in FIGS. 1 to 7, wherein FIGS. 1 to 7 are schematic top views of the process flow for a wafer redistribution process.
As shown in FIG. 1, a wafer 100 comprising a plurality of bonding pads 102 is provided. A protection layer 104 that is disposed over the wafer 100 and exposes the bonding pads 102 is also formed over the wafer 100. A titanium layer 106 and a copper layer 108 are sequentially formed over the wafer 100 surface. As shown in FIG. 2, a patterned photoresist layer 112 is formed over the surface of the copper layer 108, wherein the patterned photoresist layer 112 comprises a plurality of openings 112a, which expose a part of the copper layer 108. Thereafter, a copper layer 109 is electroplated on the surface of the exposed copper layer 108.
Referring to FIG. 3, the patterned photoresist layer 112 is then removed. Further using the copper layer 109 as a mask, portions of the copper layer 108 and the titanium layer 106 are etched to form a patterned trace layer 150. As shown in FIG. 4, a patterned benzocyclobutene layer 114 is formed over the protection layer 104 and the patterned trace layer 150. This patterned benzocyclobutene layer 114 comprises a plurality of openings 114a, exposing the copper layer 109. A copper layer 116 is further formed over the surface of the patterned benzocyclobutene layer 114 and the exposed surface of the copper layer 109.
As shown in FIG. 5, a patterned photoresist layer 118 is formed over the surface of the copper layer 116. The patterned photoresist layer 118 comprises a plurality of openings 118a, which expose a portion of the copper layer 116. Using an electroplating method, a copper layer 120 and a tin-lead paste layer 122 are sequentially electroplated on the exposed surface of the copper layer 116. As shown in FIG. 6, the patterned photoresist layer 118 is etched. Further using the tin-lead paste material layer 122 as a mask, the exposed copper layer 1116 is removed. Thereafter, as in FIG. 7, a solder reflow process is performed to form the tin-lead paste material layer 122 into a bump 122a. 
As discussed in the above, when benzocyclobutene is used for the dielectric layer, the binding between benzocyclobutene and copper is poor. Therefore, during the processing step shown in FIG. 4, a peeling of benzocyclobutene is resulted during the development process to pattern the benzocyclobutene layer 114 on the patterned trace layer 150. The manufacturing process is thereby adversely affected.